/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.nineoldandroids.util;

/**
 * A property is an abstraction that can be used to represent a
 * <emb>mutable</em> value that is held in a <em>host</em> object. The
 * Property's {@link #set(Object, Object)} or {@link #get(Object)} methods can
 * be implemented in terms of the private fields of the host object, or via
 * "setter" and "getter" methods or by some other mechanism, as appropriate.
 *
 * @param <T>
 *            The class on which the property is declared.
 * @param <V>
 *            The type that this property represents.
 */
public abstract class Property<T, V> {

	private final String mName;
	private final Class<V> mType;

	/**
	 * This factory method creates and returns a Property given the
	 * <code>class</code> and <code>name</code> parameters, where the
	 * <code>"name"</code> parameter represents either:
	 * <ul>
	 * <li>a public <code>getName()</code> method on the class which takes no
	 * arguments, plus an optional public <code>setName()</code> method which
	 * takes a value of the same type returned by <code>getName()</code>
	 * <li>a public <code>isName()</code> method on the class which takes no
	 * arguments, plus an optional public <code>setName()</code> method which
	 * takes a value of the same type returned by <code>isName()</code>
	 * <li>a public <code>name</code> field on the class
	 * </ul>
	 *
	 * <p>
	 * If either of the get/is method alternatives is found on the class, but an
	 * appropriate <code>setName()</code> method is not found, the
	 * <code>Property</code> will be {@link #isReadOnly() readOnly}. Calling the
	 * {@link #set(Object, Object)} method on such a property is allowed, but
	 * will have no effect.
	 * </p>
	 *
	 * <p>
	 * If neither the methods nor the field are found on the class a
	 * {@link NoSuchPropertyException} exception will be thrown.
	 * </p>
	 */
	public static <T, V> Property<T, V> of(Class<T> hostType,
			Class<V> valueType, String name) {
		return new ReflectiveProperty<T, V>(hostType, valueType, name);
	}

	/**
	 * A constructor that takes an identifying name and {@link #getType() type}
	 * for the property.
	 */
	public Property(Class<V> type, String name) {
		mName = name;
		mType = type;
	}

	/**
	 * Returns true if the {@link #set(Object, Object)} method does not set the
	 * value on the target object (in which case the
	 * {@link #set(Object, Object) set()} method should throw a
	 * {@link NoSuchPropertyException} exception). This may happen if the
	 * Property wraps functionality that allows querying the underlying value
	 * but not setting it. For example, the {@link #of(Class, Class, String)}
	 * factory method may return a Property with name "foo" for an object that
	 * has only a <code>getFoo()</code> or <code>isFoo()</code> method, but no
	 * matching <code>setFoo()</code> method.
	 */
	public boolean isReadOnly() {
		return false;
	}

	/**
	 * Sets the value on <code>object</code> which this property represents. If
	 * the method is unable to set the value on the target object it will throw
	 * an {@link UnsupportedOperationException} exception.
	 */
	public void set(T object, V value) {
		throw new UnsupportedOperationException("Property " + getName()
				+ " is read-only");
	}

	/**
	 * Returns the current value that this property represents on the given
	 * <code>object</code>.
	 */
	public abstract V get(T object);

	/**
	 * Returns the name for this property.
	 */
	public String getName() {
		return mName;
	}

	/**
	 * Returns the type for this property.
	 */
	public Class<V> getType() {
		return mType;
	}
}
